Purification of gonad-stimulating substance (GSS) and its secretion mechanism during breeding season

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In starfish, oocyte maturation and spawning are first triggered by a peptide hormone (gonad-stimulating substance, GSS) present in nervous tissue. GSS was purified from radial nerves of starfish Asterina pectinifera. Although a molecular weight of A. pectinifera GSS was estimated to about 4,700 using a mass-spectrometry, the quantity was not enough to determine the amino acid sequence. This study also examined organization of neural networks in ovaries and testes of the starfish, Asterina pectinifera by employing an antibody that recognizes molecules belonging to SALMFamide family of echinoderm neuropeptides. Following incubation with a SALMFamide 1 antibody primary antibody, and subsequently with rhodamine-conjugated second antibody identified the network structures were observed in both ovaries and testes. The networks were restricted mainly to their surface and little evidence of immunoreactivity was seen inside their basement membranes. The result suggests that neural networks distributed in gonads maybe involved in the regulation of gametogenesis and gamete shedding in starfish.Furthermore, using degenerate primers derived from consensus sequences of the memmalian glycoprotein hormone (LH, FSH and TSH) receptors, we cloned cDNAs (apGPHR) from ovaries of.the starfish Asterina pectinifera. However, a partially purified gonad-stimulating substance (GSS) failed to increase cyclic AMP levels in COS-7 cells expressing apGPHR. This suggests that a new neural petide other than GSS is a ligand for the apGPHR in starfish.